The remnants of middle-status housing are seen at a site in Caral, Peru, in this undated handout photo. The dwellings consisted of rooms with walls are made of adobe. A Peruvian complex of towering pyramids, irrigation canals and apartment-like buildings may have been the Americas' first urban center, built by a civilization that thrived more than 4,000 years ago. (AP Photo/Jonathan Haas, Field Museum) less

The remnants of middle-status housing are seen at a site in Caral, Peru, in this undated handout photo. The dwellings consisted of rooms with walls are made of adobe. A Peruvian complex of towering pyramids, ... more

Photo: JONATHAN HAAS

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Mystery metropolis / Ruins of a 4,600-year-old city in Peru challenge theories of civilization

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An ancient city in a remote Peruvian valley is more than 4,600 years old - - far older than any known city in this hemisphere and old enough to rewrite the history of the New World -- according to a finding reported in the current journal Science.

"This may actually be the birthplace of civilization in the Americas," said Winifred Creamer, one of the archaeologists responsible for the discovery.

Archaeologists have long believed that when the pharaoh Cheops was building the first of Egypt's great pyramids about 4,560 years ago, the Americas were still a tribal backwater of small hunter-gatherer villages. The new finding suggests that Caral, a large city with giant pyramids of its own, may already have been decades old at the time.

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The startling conclusion, which could topple some theories about the origins of urban life, results from new, extremely precise radiocarbon dating of the obscure 170-acre site, which was discovered in 1905 but had never been dated or carefully studied.

Dating shows that parts of Caral, in Peru's remote Supe valley, were built as early as 2627 B.C., which makes it about 1,000 years older than the oldest known city in the Americas. The pyramid of Cheops, the largest and earliest of the Giza pyramids in Egypt, was finished around 2560 B.C.

The findings were made by Creamer and her husband, Jonathan Haas of Chicago's Field Museum, and a Peruvian colleague, Ruth Shady of San Marcos University in Lima, who has been working at the site with her students for about four years.

Caral's center is a huge, sunken circular plaza, more than a third of a mile across, surrounded by large stepped pyramids which have crumbled around the edges so they appear now as rounded mounds. The largest is 65 feet high and larger than a football field. Next to the pyramids were complexes of high- status dwellings of stone with large rooms and fine plaster walls, while farther out the archaeologists uncovered areas with medium-status and lower- status residences, smaller and made of mud and canes.

The pyramids were built with stone retaining walls, which were filled in with rubble and river rocks, carried in woven bags made from reeds. The bags were thrown in along with the rocks, and it was the reeds from these bags that allowed the construction to be dated so precisely.

Haas suggested that the discovery will force archaeologists to rethink their theories of how civilization began in the Americas. While archaeologists used to believe that no urban centers appeared anywhere in the world until the domestication of grain made large-scale central storage of foods possible, that theory has been crumbling in recent years with the discovery of some urban sites in the Middle East and elsewhere that seem to predate grain cultivation. But this is the first site in the Americas to do so.

Caral lies in a narrow valley, about 14 miles from the coast. Rather than large-scale growing of food crops, the archaeologists said, Caral apparently had an extensive irrigation system, but primarily for growing cotton and gourds. Much of the cotton was apparently traded with coastal residents to make fishing nets, while the fish may have been a major staple for the inland residents. Some crops were apparently grown, including avocados, beans, peanuts and squash. Seafood, including sardines, anchovies and mussels, may have been their primary food, as indicated by remains found at the site.

Ironically, although it may have been the urban center of the Americas in its heyday, the Supe valley soon receded in importance and has never since had significant human settlements.